Lost and dont know what to do.

I have a 2007 Peterbilt 379 with C15 MXS Acert. I have only had this truck 5 months and have had so many problems but the present issue is I had injectors 4,5, and 6 go out all at the same time. Injector #6 was in the worst shape but 4 and 5 was not much better. I replaced wth aftermarket injectors from Heavey Highway parts , run the overhead and also replaced the riser pump while i had the truck down.
The fuel psi is at 90lb and with two new turbos im getting 51 lbs of boost but the motor is fluttering and cutting out at low rpm and low boost. Once I am able to get up to 65 to 70 mph the fluttering and cutting out stops and seams to be running ok but its just getting to that point thats the problem . I am going to be replacing the clutch if i dont fix this issue soon.
I have had the truck in and out of my Cat shop and they have tried eveything from new ECM to check valves, fuel reg., boost sen. and disconecting the air compressor supply from the block thinking it may be pulling boost.
I am lost and loosing money fast . I really need help. If anyone has had this problem or any ideas im in real need and would be so grateful .

 

Just ideas: I don’t know much about the cats and where the pressures should be but I would be checking all your grounds and power to the ECM. If the ECM is getting an unstable power supply, there could be some chance in creating this symptom.

Also since it has to do with speed. Wonder if the accelerator pedal/ sensors/ wiring have anything to do with it. Because I’m pretty sure the injectors receive their command from the ECM which receives input from the pedal. So there may be a disconnect in that system somewhere. Just maybe.

Then when they installed the ECM hopefully they put the right program in, because that could mess up the timing and injection angles or not match the size injectors you have and etc

Then. You got the flow of fuel. Maybe your getting air into the fuel somewhere. See if you can find a flow chart or a flow map of that make and model truck or for the engine or both and study that good and see if anything sticks out. Study where the fuel starts, and follow it to each next stop along the way.
Good luck

 

Did they take a close look at the camshaft and valve train?

Any boost leaks?

What makes them think the injectors 'went out'? Did they bench test them when they removed them?

 

Just wondering if they put it on a dyno and under load watching the sensors. I had a truck, 2016 Mack - MP10 that just out of a blue had a failed injector then it turned into a nightmare and finally convinced Mack dealer to put it on the dyno and run it heavy for 15 minutes at highway speed and the cause finally popped up, and they traced it back to the ECM wiring harness. That was replaced and it has not given me any issues since.

 

My truck had a inframe 168000 miles ago but they put all the original injectors back in the truck . All that was done was a cut-out test before 4,5, and 6 injectors was pulled and 4 and 5 was very weak and #6 you could tell no change in idle under a load. I am starting to wounder if they sent me the right injectors in the first place. Carolina Cat is one of the best Cat truck shops around here and they have went over all the fuel system and tells me all is within spec.
I dont know enough to even get myself in trouble but these guys do and they are having no better than i have had trying to pin piont the problem and its getting bad.
Thanks for all the idea's and i will try to relay what I have learned . Thanks again.

 

Well i am still hemorrhaging money on this mxs and truck is still in the exact same shape. Caterpillar has pulled all injectors put new O-rings on them, redo the overhead, I put the updated spring in the new T pump, all new check valves fuel pressure is at 90 PSI idle and the twins are putting out about 51 lb. Caterpillar put a new ECM on the truck and that didn't fix the problem. All new check valve, every plug-in connection on the truck has been thoroughly cleaned and owmed and everything seemed to be up to spec from what I'm being told by my cat technician. But the truck is still fluttering and cutting out low RPMs low gears. Cat does not have access to a Dino in Asheville but every Tech they have in the shop as been on this truck trying to figure it out and after 2 months I am almost to the point of filing bankruptcy. If anyone else is that this issue please let me know what being. I know it's going to end up something simple but right now it's costing me a world of money.

 

Try talking to service at Cleveland Bros. Cat in Turbotville PA. Years ago they had a man who was unbelievable at solving oddball problems. I can’t recall his name.

 

Maybe look into rawze.com

 

You need to post this in the other trucks forum. The main page. A lot of people don't seem to look in this section as much. There are some good cat guys here. Or try Facebook cat engine masters 3

 

I agree with ridgeline gotta figure out a way to get it dyno'd under a load